Wave-division multiplexing (WDM) is a type of multiplexing in which two or more optical carrier signals are multiplexed onto a single optical fiber by using different wavelengths (that is, colors) of laser light.
Bandwidth is the data transfer capacity of a link or connection (also referred to as a “path”), which may be expressed in optical data units, bits per second, number of time slots, or expressed by other methods.
In many optical transmission systems, such as p2p networks, there are (1) working connections within the network having multiple nodes and communication links for transmitting data between a headend node and a tailend node; and (2) protecting connections specifying a different communication links for transmitting data between the headend node to the tailend node in the event that one or more of the working connections fail. Working connections may also be referred to as working paths. Protecting connections may also be referred to as recovery paths and/or protecting paths and/or protection paths. A first node of a path may be referred to as a headend node or a source node. A last node of a path may be referred to as a tailend node or end node or destination node. Typically, the headend node (the active node) initially selects to receive data over the working connection and then, when a working connection fails, the headend node selects a protecting connection for passing data within the network. The set up and activation of the protecting connections may be referred to as protection. Protection mechanisms, where network resources act as backup for working connections, have been in use for some time.
However, in single fiber transmission, bidirectional or counter-propagating receiver (Rx) and (transmitter) Tx wavelengths travel on the same fiber. If a reflection coming from an end of a cut or disconnected fiber is mistaken as a valid signal at the optical detector, no protection switch may be performed.